Pulse oximetry provides a measure of the oxygenation in arterial blood. Regional oximetry, sometimes referred to as tissue oximetry can provide a measure of organ health associated with oxygenation of the organ tissue. These different measurements of oxygenation are determined using emitted light of different optical wavelengths and using different algorithms. For example, with pulse oximetry, arterial blood exhibits a pulsatile behavior which facilitates measurement of oxygen content. On the other hand, pulsatile behavior of a signal associated with the cerebellum does not facilitate measurement of oxygenation in the brain.
Clinical systems provide a measure of both pulse oximetry and regional oximetry using a variety of optical sensors that interface with a processor. A clinical system can be powered by metered line service and, in some instances, using multiple processors.
In field settings, however, the power demands to provide both pulse oximetry and regional oximetry have resulted in devices that are rather large and suffer poor battery life.